pop sound every 45 or so from my HT audio system

[Booker]

I recently started to hear a "pop" like when you turn the system on, or you plug to any AV system... witht he audio ON...this happen when the System is ON but no matter the Input..it could happen when is coax signal or Optical signal...

is not often.. sometimes 40 min or more... but is starting to anoy me

It is not a ground loop either coz i don´t own Ground on my room...

is weird, coz the only thing i change was the RCA Cable from my PC to the Reciver... It has a 2feet cable before and i changed for a 5 feet one.

At first i though it was the cable but then i was watching a Movie with a Coaxil Input on.. and the pop did it as well... the PC was even turned OFF.

is posible the cable alone is doing this? even when the PC is not ON and the Active input is other than the PC cable?

[Stoney]

You might try disconnecting all inputs to the amp and running it idle to see if it still does it (if it is a receiver, maybe run the FM so it has a signal). If the POP doesn't happen with the AMP alone, connect your inputs one at a time and try to isolate which one may be causing the problem.
There is also the possibility that it is coming in on your AC line.

[aud19]

It is possible that it's the cable, try swapping it back with the previous one and see if the problem continues. Otherwise Stoney's suggestion to try each input is the next best thing to try.

You could also have static build up in the receiever, a wire from the chasis to the screw on your electrical ooutlet might help that

[chrispy35]

Did you add a bar fridge in the room? Inductive loads turning on and off can cause a pop like you mention (did for me). Try to figure out what else is on the circuit, it may lead you to something you hadn't thought of.